It's not every day that you see a cosmologist unload on a historian
with "righteous" indignation, but that is what has been happening over at

*Letters to Nature*(initially in January but also stretching into*February*). What a fuss about Bayesian probability! – I wonder, what was the likelihood of that?
I see this as further evidence that Barnes is (probably)
uncloaking some more because he has drawn attention to the fact that, two years
ago, he was arguing with Richard Carrier for an argument in favour of NID, or
"non-terrestrial intelligent design".
He didn't do this unknowingly.
Here's an extract from one of his comments:

One more question. I won’t make
any claims. I’ll even make it multiple choice. Just give me your main argument
against fine-tuning in probability notation.

Let

o = intelligent observers exist

f = a finely tuned universe
exists

b = background information.

NID = a non-terrestrial
intelligent designer exists.

Here’s the question.

1. In probability notation, what
follows about the posterior probability of NID from the fact that p(f | o) = 1?

Multiple choice:

a) p(NID | f.o.b) / p(~NID |
f.o.b) = 1

b) p(NID | f.o.b) / p(~NID |
f.o.b) = p(NID | b) / p(~NID | b)

(Does this follow from footnote 29?)

(Does this follow from footnote 29?)

c) p(NID | f.o.b) / p(~NID |
f.o.b) = p(NID | o.b) / p(~NID | o.b)

(if o is part of b, is this option equivalent to the previous one?)

(if o is part of b, is this option equivalent to the previous one?)

d) p(NID | f.o.b) / p(~NID |
f.o.b) is independent of p(o | ~NID) – the probability that a life permitting
universe would exist by chance. Thus, even if p(o | ~NID) << 1, this fact
is irrelevant to the posterior probability of NID.

e) Some of the above. Please
specify.

f) None of the above. Please
answer in probability notation.

So, he (Barnes) is fully cognisant of the fact that his
fine-tuning argument is essentially an intelligent design argument.

It's interesting that he should be so keen to faff around
with Bayesian probability when his speciality is apparently star formation (or
some such). These sorts of arguments
have primarily been the preserve of philosophers, and quite often apologists (and, as a consequence, anti-apologists).

---

On the topic of Barnes' faffing about with Bayes, he wrote a
piece called

*10 Nice things about Bayes' Theorem*. I too have dabbled in*Bayes' Theorem*, primarily because of*WLC's abuse*of it, which means that it relates to the resurrection thing, rather than the fine-tuning thing.
Barnes had a go at Carrier, in a

*comment from two years ago*, in which he wrote:
* “all prior probabilities are
the posterior probabilities of previous equations”.

Learn to use probability
terminology correctly, please. Don’t talk about the probability of an equation.

Interestingly, in his 10 nice things piece, Barnes wrote:

Today’s posterior becomes
tomorrow’s prior. Hence,

*Bayesian updating*.
This is basically exactly what Carrier was saying, although
in the eyes of a hostile witness, he was apparently talking about Pr(equation)
rather than the probability that falls out of an equation like
Pr(A|B)=Pr(B|A).Pr(A)/P(B) – the probability associated with that equation,
perhaps, if not "of" as in common parlance.

Strange.

Perhaps Barnes just doesn't like to call Pr(A|B)=Pr(B|A).Pr(A)/P(B)
an equation which is still strange, because it acts precisely like an equation,
with multiplication and division, and in some cases there are additions and
subtractions in Bayesian calculations – just like in real equations. Still, it does sound like he was grasping
desperately at straws.

I wasn't that keen to slog through Barnes' most recent
attacks on Carrier, but after noting this little own-goal on his part, I'm now
a little more intrigued.

---

Note that Carrier
has since replied,

*here*.
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